The index fell to that level even after President Donald Trump told Bloomberg News just before 1 p.m. EDT that he was "looking at" breaking up the big banks. The major U.S. stock indexes, led by bank stocks, declined suddenly on Trump's remarks before rebounding in a volatile trade.

But by the end of the day, the unexpected comments from the president didn't cause more people to buy protection in the options market from a market drop, something the so-called Vix measures.

Monday marked the second time this year the Vix has traded below 10, the first being Feb. 1. The index broke below 10 for less than a minute after a Federal Reserve monetary policy decision was announced.